1. Field of the Invention
This invention relates to an alkaline detergent for an automatic analyzer, to a cleaning method for the automatic analyzer, and to the automatic analyzer.
2. Description of the Related Art
To clean the reaction tube to which a reaction solution of sample and reagent contacts in an automatic analyzer, there has been proposed the employment of a cleaning solution comprising an alkaline solution containing a nonionic surfactant for enhancing the detergency thereof. It has been proposed in this case to employ polyoxyethylene alkylether which is excellent in detergency as a nonionic surfactant. It has also been proposed to employ a mixture of plural kinds of polyoxyethylene alkylether differing in number of moles of oxyethylene included therein.
A cleaning solution of this kind has a cloud point (a temperature inducing whitening of the cleaning solution as the temperature of cleaning solution is increased) representing one of the properties of the surfactant, thereby occasionally raising the problem that the cleaning solution may be whitened and segregated due to the heat generated in the automatic analyzer. Meanwhile, there has been proposed a cleaning solution which regulates the cloud point of cleaning solution to a predetermined range so as to secure a sufficient detergency. In this case, since the cloud point is confined to the vicinity of working temperature, it is assumed that the cleaning solution is whitened and rendered non-uniform under the working condition. Further, there has been also proposed to employ a cleaning solution which is diluted using an organic solvent to enhance the detergency thereof without damaging to the reaction cell.
Generally speaking, a detergent containing a surfactant is whitened at the cloud point thereof. This cloud point is known to vary depending on the alkalinity of the solution, the kind of surfactant and the concentration of surfactant. However, in order to increase the alkalinity of the solution so as to enhance the detergency to smears of proteinic residue, it has been considered inevitable to regulate the concentration of surfactant to a lower level. An alkaline detergent is usually diluted with pure water on the occasion of using it in an automatic analyzer. In order to secure the content of a surfactant at a predetermined level of concentration after this dilution, the dilution magnification is controlled to a lower level. Namely, the alkaline cleaning solution usually n comprises the alkaline detergent at a concentration of as high as about 10% by volume. As the throughput capacity of the analyzer is increased, the quantity of cleaning solution to be employed also increases, thus increasing the frequency of exchanging the detergent.
Although it may be possible to avoid this increase in frequency of exchanging the detergent by using a larger detergent vessel, a detergent vessel having such a large capacity is very difficult to handle. Moreover, as the detergent vessel is increased in capacity, the space occupied by the detergent vessel in the automatic analyzer is also increased, thus leading to an increase in scale of the analyzer.